We are testing hypotheses about the synaptic organization of the stomatogastric system of crustaceans and the meaning of this organization for the production of motor patterns. These hypotheses are based on an extensive description of this organization. We are studying the sensory modulation of these patterns, and analyzing the neuronal networks of the ganglion with a digital-computer model to examine the significance of synaptic dynamics for features of the motor patterns. We are studying the structure of stomatogastric neurons, and measuring their membrane resistances, input resistances and voltage attentuation to quantify these properties important for synaptic integration. We are also exploring the interactions of command and sensory input to the swimmeret system, to see if principles developed in the stomatogastric system can be extended systematically to more complex nervous systems.